No power between 3k-4.5k

[PCH82]

Hello all

I have a '82 gs750T. I pulled out out of some guy's backyard for $400. Over the past month or so I rebuilt the carbs, cleaned the gas tank, and replaced the stator. It starts right up, idles fine, and runs great at low RPMs. Between 3k and 4.5k it bogs, stumbles, and occasionaly backfires. When I rev it in neutral it still bogs at 3-4.5k even with the throttle wide open. Sometimes it tries to die if I nail the throttle in that rpm range in neutral. Once it hits 4.5k it runs like a stripe-assed ape. The pilot needles are all 1.5 turns out, it has new NGK plugs, and I looked for air leaks with starter fluid and found none. The bike has 18k miles, and there is some RTV sealant around the valve cover gasket, so I assume one of the POs adjusted the valves at some point. It doesn't seem to have any valve noise. Any ideas on where to start?

Thanks,
Pat

[outlawfox13]

Does it have stock exhaust, air box? And I would check valve clearence. And has the bike been jetted?
I am sure some more exp. people will be along soon, but I would start with these suggestions. Mike

[PCH82]

It has the stock exhaust and air box. As far as I know the jets are stock, but the pilot needle caps were drilled out when I got it so it's possible the carbs were messed with.

[Matchless]

Not sure what your airbox looks like, but a few weeks back I had a GS1000G with only the rubber snorkel missing at the back of the airbox doing exactly the same thing. Fitted a snorkel and she smoothed out immediately.

Check that your airbox does not leak anywhere sides, filter and rubber boots.

[PCH82]

Well that was easy. When I got the bike I took out the air filter because it looked nasty. I just remembered and put it back in, now it runs great. Would would have thought that an engine would run better with a nasty old filter than without one.

This thing is awesome, too bad the highway patrol only administers permit tests on Fridays. Today is one of a rapidly shrinking number of beautiful days left in the season and I just want to ride.

[outlawfox13]

Yea these bikes require the correct air flow, to run. If not then they need to be jetted. Happy rididng.